Color channel packing missing & 0xFF after >> 14 extraction — upper
bits bled into adjacent channels causing broken particle fading.
Same class of bug as the alpha output fix earlier.
Added particle_sse_reference.zig (faithful recreation from commit
574f96f) as a separate compilation unit for correctness comparison.
Faithful recreation of RenderSpriteQuads (0x5A0F50) with hoisted
invariant division and inlined DisplayMode_CalculateOffset. No
measurable improvement — cost is dominated by getAdapterInfo (7
sub-calls to D3D device per invocation × 3203 calls/frame) and
DrawPrimitive/DrawIndexedPrimitive virtual dispatch.
Added decompilation and assembly dumps for future reference.
Faithful recreation attempt of SetupParticleRendering (0x7B3D20).
All game function CCs verified from assembly. Vertex buffer setup
works (8 verts produced), but D3D draw submission doesn't produce
visible output. Disabled pending investigation of GfxDeviceMethod
param struct layout. The function remains as timing-only pass-through.
Fixes found during work:
- max_particle_sprites global: 0xCF58F4 → 0xCF5B60
- billboard_matrix global: 0xCF5898 → 0xCF5888
- index_buffer_6/12: 0xCF58D0/D4 → 0xCF5BAC/0xCF5AF4
- BuildIndexBuffer takes renders_count not field_28
- Identity matrices must be mutable (game writes to them)
- V4 store (vmovups) writes xyz+color as one 16-byte op instead of 4
scalar stores. Unaligned but still 1 μop on modern CPUs.
- inline for unrolls 4-vertex loops, letting LLVM schedule stores
across vertices and fill pipeline bubbles.
- Hoisted world_pos to locals to prevent array re-reads.
- A/B: BASELINE ~433ms → CUSTOM ~299ms (~31% per-period reduction).
Total from original: 520ms → 299ms = 42% reduction.
- Detected interleaved 24-byte vertex layout: xyz(12)+color(4)+uv(8).
Fast path writes 6 sequential u32s instead of scattered stores.
- Normal stride=0 (shared global) — write once in writeback, not 4x.
- Added stride_info export + logging for vertex layout analysis.
- A/B: ~30% peak reduction, baseline also improved due to less overhead.
- VBState caching on all 5 vertex paths (was only 2D and sin/cos).
Eliminates pointer re-reads: load once, emit 4 vertices, writeback.
- Cache setupRender() result per-frame via static + resetParticleCache()
called from worldUpdateDetour. Saves ~7K function calls/frame.
- @mulAdd throughout for FMA codegen on vertex position and texcoord.
- A/B verified: BASELINE ~521ms → CUSTOM ~387ms (~25% reduction).
- Inline calcColor: eliminates function call, allows OoO overlap of
cache misses on colorCtx with vertex math. Pow path falls back to
game function.
- Inline mat*vec3 transform: V4 FMA chain replaces call to 0x7BCA80.
- VBState: cache VB pointers/strides in locals, write back once after
4 vertices. Eliminates ~80 pointer re-reads per particle.
- @mulAdd throughout vertex loops for FMA codegen.
- A/B verified: BASELINE ~470ms → CUSTOM ~382ms (~20% reduction).
Full recreation of RenderParticleSprites (0x7B2A50, 2688 bytes) in
particle_sse.zig. All 5 code paths: 2D billboard, 3D billboard,
2D+rotation (sin/cos), 3D+rotation (axis-angle matrix), tail particles.
Key fixes during verification:
- colorCtx address: removed Ghidra's spurious -0x12 offset
- calcColor arg2: pass raw u32 from emitter+0x1A8, not truncated
- Texture coord lookups: +8 offset to match assembly's eax increment
between position and texcoord reads in the vertex loop
Verified in-game: particles render identically in CUSTOM vs BASELINE.
Next: optimize with SSE (inline calcColor, V4 vertex math).
- Ghidra C decompilation of RenderParticleSprites (422 lines) and 5
helper functions (calculateColorValues, matVec3Transform, etc.)
- particle_sse.zig with calcColorValues_SSE (10.7x bench but cache-miss
bound in-game — needs inlining into full function replacement)
- Bench harness for calcColorValues with correctness check
- build.zig: particle_sse as separate ReleaseFast compilation unit
- colorDetour reverted to pass-through (SSE has no in-game effect due
to L1 cache misses on scattered ColorCtx structs)
MarcelineVQ